High-throughput whole-genome analysis is becoming a standard laboratory approach for investigating cellular processes. Next-generation sequencing is replacing microarrays as the technique of choice for genome-scale analysis, because it offers advantages in both sensitivity and scale. The June issue of Cold Spring Harbor Protocols features Native Chromatin Preparation and Illumina/Solexa Library Construction from Keji Zhao and colleagues at the National Heart, Lung and Blood Institute. The article describes sample preparation for sequencing of chromatin-immunoprecipitated DNA (ChIP-Seq) to analyze histone modification patterns using native chromatin and the Solexa/Illumina Genome Analyzer. Step-by-step instructions are given for purification of human CD4+ T cells from lymphocytes and chromatin fragmentation using micrococcal nuclease (MNase) digestion, followed by chromatin immunoprecipitation (ChIP) and construction of a library for sequencing.